1. Field of the Invention
The present invention relates to a process for manufacturing trim panels for motorvehicles and to the panels thus obtained.
Many types of processes are known for the manufacture of trim panels for interiors of motorvehicles. Generally, said processes envisage to produce first of all the base portion of the panel and then to apply additional elements thereon such as door handles and pockets, that are separately prepared.
Furthermore, methods are known envisaging to directly obtain a base portion without handle and pocket, but already provided with areas covered with a fabric to improve the general appearance of the panel. Said solution, which allows to avoid the subsequent application of additional small panels covered with fabric, has been described, with different features, in several patent applications in the name of the present applicant.
EP-A-0290399 (FIAT AUTO SpA) discloses a trim panel that is obtained by securing to a base panel having missing portions a plurality of complementary panels separately prepared, a pocket and a handle. The base panel is obtained by injection molding of a single plastic material.
U.S. Pat. No. 5,167,896 (Hirota) discloses the coinjection of a resin surface material and a core of fiber-reinforced resin mixture to manufacture a cabinet for use with a display. Only a portion of the obtained cabinet has a sandwich structure with inner core and two external layers. In fact,coinjection is not an easy process and it becomes even more difficult to control where the required molded article has a geometrically complex shape such as that of a trim panel.
2. Objects of the Invention
The object of the present invention is to propose a trim panel that can be manufactured with a reduced number of operations and therefore with reduced manufacturing costs. A further object is to provide a process of preparing such panel.
Said objects are obtained by means of the present invention that relates to a process of preparing a trim panel provided with a sandwich-type structure, comprising the following steps:
injection molding a first panel base portion that is one-piece with handle and/or pocket or similar undercut parts and has missing portions located at least in correspondence to said handle or pocket or undercut parts of the panel, by coinjecting an external surface material and an inner core material into a mold provided with a cavity corresponding to said first base portion, said coinjection molding being carried out by separately heating and plasticizing the external surface material and the inner core material, feeding said materials to separate feeding ducts, independently heated, extending into the wall of said mold, feeding said materials through said ducts to one or several injection nozzles positioned inside the said mold wall, adjacent to or spaced from the said cavity of the mold, and simultaneously or successively injecting said surface material and inner core material in a fluid state into said cavity to form a sandwich-type panel base portion;
separately preparing one or more complementary panel portions having area and shape substantially corresponding to those of said missing base portions; and fastening said complementary panel portions to said first panel.
According to a preferred embodiment, two or more injection nozzles are used and the mold is locally heated to maintain the injected materials in a fluid condition until they meet inside the mold cavity and form a single panel. The invention also relates to a trim panel for autovehicles comprising a first panel base portion provided with missing portions located in correspondence of at least a handle or a pocket that are in one-piece with said first base portion, and one or more complementary panel portions separately produced and bound to said first panel base portion in correspondence to cited missing portions of the panel; said first panel base portion being essentially consisting of two external layers of surface material and of an inner layer of core material arranged in a sandwich arrangement, said surface material and said core material being coinjected in a mold through one or several injection nozzles to obtain said first panel base portion.
According to a preferred aspect of the invention, said missing portions of the first panel base portion obtained by co-injection molding are located in correspondence to the areas where, in the finished panel, there is provided an undercut, namely in correspondence to the door handle and the panel pocket. During the molding step a gas injection may be performed in correspondence to localized areas of the panel such as for instance handle, pocket, ribs or other areas where shrinkage may occurr.
The missing portions of the panel are manufactured separately, in a known way, and are preferably consisting of small panels covered with fabric.
The invention will be now described in a more detailed way with reference to the accompanying drawings given by illustrative and non limiting purposes, where: